[praka123]

well i found this gentoo forum thread useful for all amd-64 users and aspirants
http://forums.gentoo.org/viewtopic-t-221361.html

mplayer / xine dont play some movies , *.wmv/*.rm/win32codecs dont work
A: You need 32bit mplayer to use 32bit codecs (for stuff like wmv9 and real). No win64codecs are currently availible.
Take a look at this guide and this topics: xine thread or this mplayer thread or just search for "mplayer" in amd64 forum what will answer your questions on this topic more completely. 32bit realpayer also works on amd64 if you want to play *.rm files.
See here what gentoo-wiki has to say about it.

below wiki article also may hold great use:
http://gentoo-wiki.com/HOWTO_AMD_64